Electricity: circuit makers and breakers – Electric switch details – Actuators
Reexamination Certificate
1999-12-16
2001-07-31
Scott, J. R. (Department: 2832)
Electricity: circuit makers and breakers
Electric switch details
Actuators
C074S503000, C074S504000, C200S529000, C200S538000
Reexamination Certificate
active
06268577
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to electromechanical switches and, more particularly, to a push-pull switch operator.
BACKGROUND OF THE INVENTION
A push-pull switch is commonly used as a manually operated controller for industrial electric motor control circuits. A push-pull switch is typically mounted in a front panel of a control enclosure. Push-pull switches are used in applications where push and pull actuation of the control circuit is desired, as opposed to single push button, rotary selector switch or knife switches, for example. A push-pull switch has a cap that actuates an electrical switch to open and close electrical circuits.
Prior push-pull switches used spring-loaded ball bearings to pop into side grooves. The cap was directly linked to a pushing part that actuated the electrical contact blocks. The ball bearings detented into side grooves, locating the position of the linkage to an in position, a middle position, or an out position.
Because of the direct linkage used in prior push-pull switches, switch contacts could move only about half of the distance normally travelled by a conventional push-button operator in moving from middle to in-positions, or middle to out-positions. This reduced the open air gap in the contact blocks, forcing a reduction in ampere rating for a standard contact block or the use of special early-make or late-break contact blocks. The use of a direct linkage also required that all contact blocks used with the push-pull switch operate simultaneously. This reduced the application options for individual push-pull switches. Also, spring-loaded ball bearings can be difficult to assemble.
The present invention is intended to overcome the problems discussed above, in a novel and simple manner.
SUMMARY OF THE INVENTION
In accordance with the invention a push-pull switch uses indirect contact actuation.
In accordance with one aspect of the invention there is disclosed a push-pull switch operator including a housing. A rotary drive is rotationally mounted in the housing and has a circumferential cam track. An actuator is operatively coupled to the rotary drive for converting linear movement of the actuator to rotary movement of the rotary drive. A pusher is received in the housing and has a follower pin riding in the cam track to convert rotary movement of the cylinder to linear movement of the pusher. The pusher actuates an electrical switch, in use. A cap is operatively coupled to the actuator for manually operating the actuator between in, middle and out positions to selectively operate the pusher.
It is a feature of the invention that the rotary drive comprises a two-piece assembly having a driver operatively coupled to the actuator whereby linear movement of the actuator is converted to rotary movement of the driver and a cam operatively coupled to the driver for rotation therewith and the cam track pattern is provided on the cam. A torsion spring biases the cam in the housing so that the actuator is normally in the middle position.
It is another feature of the invention that the actuator comprises a cylinder including a helical slot and the rotary drive is telescopically received in the cylinder and has a driver-arm received in the helical slot. The housing has a circumferential slot receiving the driver-arm to constrain linear movement of the rotary drive.
It is a further feature of the invention to provide a second pusher received in the housing and having a follower pin riding in the cam track to convert rotational movement of the cylinder to linear movement of the second pusher. The second pusher actuates a second electrical switch, in use. The cam track is configured to operate the two pushers in opposite directions. The cam track comprises oppositely-oriented helical tracks.
It is another feature of the invention that the driver-arm extends radially outwardly from a flexible arm. A spring in the rotary drive prevents inward deflection of the flexible arm.
It is yet another feature of the invention to provide an apron snap fit to the actuator and surrounding a front end of the housing. A ring gasket surrounds an outer wall at the front end of the housing and contacts the apron for sealing the housing. The ring gasket is formed of rubber and includes a wiper seal.
There is disclosed in accordance with another aspect of the invention a push pull switch operator including a housing. A drive assembly is movably mounted in the housing and has a cam track. A cap is operatively coupled to the drive assembly. The cap is manually, linearly actuable between in, middle and out positions. A pusher is received in the housing and has a follower pin riding in the cam track. The cam track is configured to convert linear movement of the cap in one direction to linear movement of the pusher in an opposite direction. The pusher actuates an electrical switch, in use.
Further features and advantages of the invention will be readily apparent from the specification and from the drawing.
REFERENCES:
patent: 2800806 (1957-07-01), Sangster
patent: 3581036 (1971-05-01), Dennison
patent: 4255633 (1981-03-01), Johnston et al.
patent: 4282414 (1981-08-01), Johnston et al.
patent: 4902865 (1990-02-01), Muller et al.
patent: 5408061 (1995-04-01), Martin
patent: 5605225 (1997-02-01), Schaeffer
patent: 5684670 (1997-11-01), Zimmermann et al.
patent: 647954 (1995-04-01), None
Marquardt Terry L.
Zimmermann Rudolf E.
Scott J. R.
Siemens Energy & Automation Inc.
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